Chronic deep brain stimulation (DBS) is becoming an established neuro-surgical procedure in the treatment of movement disorders, and is now often used in place of the conventional approach of lesioning or ablation. DBS typically entails chronic implantation of a stimulating electrode (referred to herein as a lead) specially designed to apply energy from a pulse generator that is implanted beneath the skin. Ablative procedures (a.k.a., lesioning) typically involve acute insertion of a lead specially designed to apply energy from an external radio-frequency (RF) generator. Lesioning and DBS have similar efficacy in the treatment of movement disorders. While lesioning causes permanent destruction of the target cells, DBS reversibly inhibits or excites cells.
When compared with ablative procedures, DBS seems to have an improved side effect profile. As with any implanted system, DBS therapy involves certain issues related to the therapy and to the DBS hardware. Patients with chronically implanted DBS leads can encounter complications requiring hardware revision or removal. For instance, DBS devices can introduce infection, erode through the skin, fracture, migrate, short-circuit, or physically disconnect. In some instances, e.g., of skin erosion or infection, the DBS lead may need to be removed even though it continues to produce important clinical benefits.
When the DBS or other brain stimulation lead is removed, patients experience loss of therapeutic benefit and increased disability. Generally after a time delay, surgical options may include either repeated lead implantation or a lesioning procedure. Another scenario in which lesioning may be considered occurs in patients who develop a tolerance to stimulation, such as those with essential tremor who develop a tolerance to DBS, and therefore lose therapeutic effectiveness. Data shows that up to 50% of DBS patients with essential tremor develop a tolerance to DBS. Such patients may require progressively increasing current output for treatment (e.g., tremor suppression), leading to battery failure and/or frequent and impractical battery replacements.
It has been suggested to use a DBS lead for lesioning. See, for instance, Kumar, et al., “RF Lesioning through an Implanted Deep Brain Stimulating Electrode Treatment of Tolerance to Thalamic Stimulation in Essential Tremor” Movement Disorders 2000;15 Suppl 3:69. However, there are several problems with the approach described. For instance, the authors indicate that the RF parameters required to create the lesion were determined using egg white. While this is indicative of appropriate parameters, a more definite approach would be beneficial. Furthermore, the authors state that “RF lesioning can be safely performed through an implanted DBS electrode. This is an effective treatment . . . ” The efficacy of the procedure is questionable without feedback that ensures the temperature reaches that required to create the lesion(s), while the safety of the procedure is questionable without feedback that ensures the temperature does not exceed that required to create the lesion(s), which could cause destruction of cells in a larger area than desired during the procedure.
A similar approach to lesion creation with a DBS electrode was described in an article of the present inventor and his associates. See Oh, et al., “Deep Brain Stimulator Electrodes Used for Lesioning: Proof of Principle” Neurosurgery 2001 August; 49(2):363-369. As pointed out by the authors, “temperature measurement is not available when using a DBS electrode for RF lesion generation.” Filed shortly after publication of the Oh, et al. article, US Patent Application 2003/0083724 A1 describes a specific configuration of multichannel electrode, designed to perform recording, stimulating, and lesioning. It may further provide imaging capability and/or therapies such as drug or radiation delivery. Yet again, the described device lacks the capacity to measure temperature, limiting the efficacy and safety of procedures using the device.